Refrigeration apparatus



Oct. 25, 1938.

L. B. M. BUCHANAN REFRIGERATION APPARATUS Filed March 50. 1935 2 Sheets-Sheet l HIGH SID FLOR-l VRLVK.

INVENTOR LESLIE B.M.BUCHRNAN BY ATTO EY L m J 1111,!!!

WRRMER couatn E'VHP. EVHP.

WITNESSES: h F"1a.3.

L. B. M. BUCHANAN REFRIGERATION APPARATUS Filed March 30.- 1935 2 Sheets-Sheet 2 PREFERRED EVRP.

THERH. OR THERPLF'OR fin.- U

PREFERRED o1- HER EVRPORATOR vnroah'rolt.

Patented Oct. 25, 1938 21133349 REFRIGERATEQN APPARATUS Leslie B. M. Buchanan, Springfield, Mass, assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 30, 1935, Serial No. 13,884

18 Claims.

My invention relates to refrigeration apparatus, more particularly to refrigeration apparatus embodying a plurality of evaporators operating at different temperatures, and it has for 5 an object to provide improved apparatus.

A further object is to provide apparatus of the character set forth having a minimum number of parts, particularly moving parts such as valves.

which the higher temperature evaporator operates at higher pressure to provide increased efficiency, and which apparatus has a minimum number of moving parts. r

i A further object is to prevent condensation of gaseous refrigerant in the lower temperature evaporator when the higher temperature evaporator is in operation at the higher pressure.

In accordance with the present invention, the lower temperature and the higher temperature evaporator, which operate at diiferent times, are connected in parallel, and the means for reducing the pressure of the condensed refrigerant, such as an expansion valve, is common to both evaporators. A valve means is provided for controlling flow of refrigerant through atleast one evaporator for selectively effecting refrigeration in either evaporator. However, the evaporators are in free communication with each other so that the pressure therein is substantially the same at all times. To avoid condensation of vaporous refrigerant in the lower temperature evaporator when the higher temperature evaporator is operating, a connection between the evaporators is arranged so that liquid refrigerant flows into and fills the lower temperature evaporator at such times.

In accordance with a further feature of. invention, the supply of refrigerant is controlled in accordance with the requirements of whichever evaporator is in operation. In one form, a thermostatic expansion valve is provided and arranged to respond to the temperature of the vaporized refrigerant in the common suction line In another form, a low side float valve is provided to maintain 'a desired liquid level for either evaporator.

The above and other objects are effected by my invention as will be apparent from the following description and claims taken in accordance with the accompanying drawings, formingapart of this application, in which:

Figs. 1 to 5 are diagrammatic views illustratin diiferent embodiments of the invention; and

Figs. 6, 7 and 8 are wiring diagrams showing Another object is to provide such apparatus in three forms of control mechanism that may be. used with any of the embodiments shown 'in Figs; 1 to 5.

Referring to Fig. 1 in detail, I show a refrigerator l having'a compartment II which is refrigerated to a relatively low temperature'by an evaporator l2, and a compartment l3 refrigerated by an evaporator 14 to a temperature which is higher than that maintained in the compartment H. The temperature in the compartment H may be below freezing, in order to freeze ice and maintain frozen articles, while the temperature in the compartment 13 may be above freezing but sufficiently low for the preservation of food. The evaporator I2 is refrigerated or oper-- ated, that is, evaporation is effected therein, at a lower temperature and at a lower pressure than the evaporator l4, and is referred to herein as the lower temperature or colder evaporator while the latter is referred to as the higher temperature or warmer evaporator. The evaporators operate at differenttimes, rather than simultaneously; each evaporator being operated at intervais for sufficient periods of time, preferably under thermostatic control, to maintain the respective temperature in its compartment.

Each evaporator may be of any desired form, either of the flooded type or of the type known in the art as a dry evaporator. In the embodiment shown in Fig. 1, the evaporator I2 is of the flooded type, comprising a header I2. The evaporator I4 is of the dry type, having a long narrow passage through which a forced circulation of a mixture of liquid and Vaporous refrigerant is effected during operation thereof. The evaporator l2 encompasses a group of ice trays [5, while the evaporator 14 is in the form of a cross-finned serpentine coil disposed in the upper portion of the compartment I3. The evaporator l4 hassuflicient cooling surface to enable it to operate with small difference between the temperatures of the refrigerant and of the air, so as to maintain a high relative humidity. in the compartment IS. The evaporators l2 and M are connected in parallel, refrigerant being supplied thereto from a common supply conduit l through branch conduits I! and I8, respectively. As will be seen from the drawings, the branch conduit ll extends downwardly from the conduit l6, while the conduit [8 extends upwardly from the conduit l5. Accordingly, liquid refrigerant supplied from the conduit 16 will flow through the branch conduit l'l into the evaporator l2 in preference to the conduit l8, when free to do so.

The evaporators I2 and M are connected through outlet conduits l9 and 2i, respectively, to a selectorvalve 22, which is adapted to place one of the evaporators in communication with a common suction conduit 23 and to cut off communication between the other evaporator and the conduit 23, so as to selectively provide flow of refrigerant through either one-of the evaporators. The valve 22 is operated in any suitable manner, for example, it may have a core 24 which is actuated in one direction by a solenoid coil 25 and in the opposite direction by a compression spring 26. In the present embodiment, energization of the coil 25 places the valve in the position for efiecting flow of refrigerant through the evaporator l4, and the spring 26 moves the valve to the opposite position for effecting fiow through the evaporator i2 when the solenoid coil 25 is deenergized.

The suction conduit 23 communicates with the inlet of a compressor 21, which may be enclosed, together with its driving motor 29, in a hermetically sealed casing. The outlet of the compressor 21 communicates through a conduit 29 with a condenser 3|. A fan 32 driven by a motor 33 may be provided to circulate air over the condenser for cooling the same. The condenser communicates through a conduit 34 with a liquid receiver 35. The latter in turn communicates through a conduit 35 with a thermostatic expansion valve 31. which discharges into the refrigerant supply conduit ii.

The valve 31 is of the type commonly known in the art as a thermostatic expansion valve. It comprises a diaphragm 33 which is, biased in closing direction by the pressure in the evaporators. It further includes a thermostatic bulb 39 attached to the suction conduit 23 and containing a quantity of volatile liquid; preferably the same liquid used in the refrigerating system. The liquid within the bulb 39 provides a vapor pressure which is a function of the temperature of the efrigerant vapor in the conduit 23 and which )ressure is imposed on the upper sideof the diaphragm 38 to bias the valve 31 in opening direction. The diaphragm 38 is also biased in closing direction by a spring 4|. The pressure on the under side of the diaphragm 33 is a function of the temperature at which evaporation takes place in whichever evaporator is in operation and the pressure on the upper side of the diaphragm is a function of the temperature of the vaporized refrigerant discharged from that evaporator, so that the difference between said pressures is a measure of the superheat of the discharged vapor. This difference in pressure operates against the spring. 4| in the direction for opening the valve 31. As the superheat tends to increase, the valve opens to admit more refrigerant, and vice versa,

thereby controlling the supply of refrigerant so as to maintain a substantially constant degree of superheat of the discharged refrigerant vapor, as is well known in the art. Such a valve controls the supply of refrigerant substantially in accordance with the capacity of the evaporator, since it admits such quantity as can be fully vaporized and slightly superheated.

The operation of this embodiment of my invention is as follows: assuming that refrigeration of the warmer compartment I3 is, to be effected, the valve 22 is positioned to place the evaporator I4 in communication with the suction conduit 23 and to cut ofi communication between the evaporator I2 and the suction conduit. Operation of the motor 29 for driving the compressor 21 and the fan 32, respe tive y, also effected. These operations are preferably effect- I ed by a thermostatic control, several forms of which will be described later. The refrigerant vaporized in the evaporator i4 is conveyed through the conduit 21, the valve 22 and the conduit 23 to the compressor, wherein its pressure is increased. It is then conveyed through the conduit 29 to the condenser 3| wherein it is liquefied. It then flows through the conduit 34 to the liquid receiver 35. From the latter, it flows through the conduit 36 to the valve 31, which regulates the flow thereof.

As the liquid refrigerant passes through th valve 31, its pressure is reduced, so that a portion of the liquid refrigerant flashes into vapor. The mixture of liquid and vaporous refrigerant is conveyed through the conduits i 6 and i8 to the'warmer evaporator I4, wherein the liquid refrigerant is vaporized in extracting heat from the compartment I3. The vaporous refrigerant is discharged from the evaporator I4 intothe conduit 2i to be recirculated.

Since the compartment I3 is maintained at a higher temperature than the compartment ll, evaporation of liquid refrigerant in the evaporator l4 results in a higher pressure in the evaporators. the evaporator l2 from previous operation thereof is condensed by the lower temperature in the compartment ll, causing refrigerant from the conduit Hi to flow into said evaporator to fill the space vacated by the vapor. Inasmuch as the conduit i1 extends downwardly from the connection with the conduits i6 and i8, the'evaporator i2 is filled with liquid refrigerant, thereby preventing any iurther condensation and heating of said evaporator.

When the evaporator i4 is in operation, the thermostatic valve 31 operates to supply such quantity of refrigerant as can be fully vaporized and superheated to a given degree in said evaporator. The relatively high temperature of the discharged vapor results in a relatively hign vapor pressure, since the degree of superheat is maintained constant.

To effect operation of the evaporator l2, the valve 22 is positioned, as by deenergizing the coil 25, to permit-flow of refrigerant through the evaporator l2 and to cut off flow of refrigerant through the evaporator l4. Operation of the motors 28 and 33 is also eifected. The operation is similar to that just described except that evaporation of liquid refrigerant takes place in the evaporator l2; the mixture of liquid and vaporous refrigerant being supplied thereto through the conduits I6 and I1, and the vaporized refrigerant being discharged from the top of the header l2 through the conduits l9 and 23 and the valve 22. The valve 31 again maintains a constant degree of superheat, but, since the temperature of the discharged vapor is lower, the

pressure in the evaporators is necessarily lower.

Since the conduit I8 extends upwardly from the conduit l6, liquid refrigerant cannot flow by gravity into the evaporator i4. The vapor in the latter is heated somewhat by the higher temperature in the compartment i3, but the pressure in the evaporators is not affected thereby.

Upon beginning operation of the evaporator l2 after operation of the evaporator I4, the former and its conduits I1 and [9 contain liquid refrigerant, while the latter and its conduits l9 and 2| contain vapor at higher pressure and liquid being vaporized which must be removed throughthe header 12 of the evaporator l2 and its conduits Any vaporous refrigerant remaining in A I! and IS in order to reduce the suction pressure. Consequently, liquid refrigerant is temporarily drawn into the suction conduit 23. A chamber 23' is preferably interposed in the latter beyond the thermostatic bulb 39 to retain said liquid temporarily. It is gradually vaporized by the superheated vapor.

In Fig. 2, I show an embodiment of my invention in which both evaporators are of the flooded type. The colder evaporator l2a is of a conventional type having a refrigerant inlet 42 at the bottom thereof and a header 43 at the top thereof. The warmer evaporator |4a is in the form of a coil having its inlet at the bottom and its outlet at the top. In this case, the conduit 36 connects the liquid receiver 35 to a float chamber 45 containing a low-side float valve 44. The float valve controls the admission of refrigerant to the float chamber. so as to maintain a liquid level indicated at 46. The upper end of the colder evaporator |2a is connected by a conduit 40 to the chamber 45 below the liquid level 46, and the upper end of the warmer evaporator Mn is connected to the chamber 45 above said liquid level. A conduit 41 extends downwardly from the lower portion of the float chamber 45 and communicates with the lower or inlet ends of the evaporators through the selector valve 22a, which may be similar to the valve 22 of Fig. 1. The suction conduit 23a communicates with the chamber 45 above the liquid level.

To effect operation of the warmer evaporator |4a, the valve 22a is actuated to provide communication between the conduit 41 and the lower or inlet end of said evaporator, while communication with the inlet of the colder evaporator In is cut off. Operation of the compressor 21 and the fan 32 is also effected. Liquid refrigerant flows by gravity from the float chamber 45 through the conduit 4! into the lower end. of the evaporator Mo to be evaporated therein. The vaporized refrigerant flows upwardly through the evaporator to the upper portion of the chamber 45, from which it is' withdrawn through the suction conduit 23a, to be compressed, condensed, and recirculated. The vapor present in the colder evaporator In at the time of change-over is compressed by the higher suction pressure and either is condensed or flows to the chamber 45.

It is replaced by liquid refrigerant from said chamber, inasmuch as the connection of said evaporator is below the liquid level in the chamber.

To effect operation of the colder evaporator IZa, the valve-22a is moved to the opposite position by deenergizing the coil 25, thereby placing the conduit 41 in communication with the evaporator |2a and cutting off communication with the evaporator Ma. As the liquid refrigerant remaining in the evaporator |4a from previous operation thereof is gradually evaporated, the suction pressure decreases and evaporation in the colder evaporator |2a begins. The compressor 21 then serves to withdraw vapor from the evaporator |2a to effect refrigeration therein.

The liquid refrigerant flows downwardly through the conduit 41 into the lower end of the evaporator, and the vaporized refrigerant flows up wardly through the header 43 and the conduit 40 to the float chamber 45, from which it is withdrawn through the suction conduit 23a. During this operation, the evaporator Mat is dry, the lower end thereof being cut off by the'valve 22a and the upper end communicating with the chamber 45 above the liquid level.

It will thus be seen that the float valve 44, in

maintaining a common liquid level for the evapo- 48, which valve operates to pass such quantity of refrigerant as is condensed in the condenser 3|. In this embodiment the evaporators are both of the dry type and the connection between the float valve and the evaporators is such that liquid refrigerant flows into the colder evaporator l2b in preferance to the warmer evaporator l4b. In. this case, this is effected by projecting a conduit 49 communicating with the float valve 48 downwardly into a conduit which connects with the inlet of the colder evaporator l2b and by connecting a conduit 52, which conveys refrigerant to the warmer evaporator |4b, to the conduit 5| at a level above the lower end of the conduit 49. In this embodiment the selector valve 22b controls communication of the outlet ends of the evaporators with the suction conduit 23b. A storage tank 53 is preferably provided in the suction conduit 23b.

Assuming first that the valve 22b is positioned to place the colder evaporator l2b in communication with the suction conduit 23b, the liquid refrigerant conveyed through the conduit 49 is free to flow into the colder evaporator. The warmer evaporator I4!) is deprived of liquid refrigerant at this time, since it would be necessary for such liquid refrigerant to rise in the conduit 5| to the connection with the conduit 52. During the operation of the evaporator l2b, there will be an excess of liquid refrigerant, since the evaporator I4!) is deprived of the same. Such excess quantity of liquid refrigerant collects in the chamber 53.

To effect refrigeration in the warmer evapo rator MD, the valve 221) is moved to the opposite position to place said evaporator in communication with the suction conduit 23b. Liquid refrigerant from the conduit 49 flows through the conduit 5| into the evaporator l2b to the extent necessary to flll the space occupied by vaporous refrigerant present from previous operation and which is now condensed due to the higher suction pressure. Further refrigerant is forced upwardly through the upper portion of the conduit 5| to the conduit 52 and then through the evaporator I411. The liquid refrigerant in the chamber 53 is vaporized by the superheat contained in the refrigerant vapordischarged from the warmer evaporator |4b. If the connecting passage is sufficiently large, some of the liquid may flow by gravity into the evaporator l4b to be evaporated therein.

In Fig. 4, Ishow my invention applied to a refrigerator 54 having food liner 55, which is divided by a horizontal partition 56 into an upper warmer compartment 3c and a lower'colder compartment H0, in accordance with the invention of M. Kalischer covered in application Serial No. 751,324, filed Nov. 3, 1934, now matured into Pat-'- 682. The warmer evaporator llc'is in the form of a serpentine coil disposed on the rear surface of the back wall portion of the food liner in heat conducting relation thereto. In this embodiment, both evaporators are of the dry type, and a thermostatic expansion valve 31c, similar tbthe valve 31 of Fig. l, is provided. Thevalve 31c discharges into a conduit 16c, and a conduit l8c extends upwardly from said conduit to the upper or inlet end of the evaporator ltc while a conduit I'lc extendsdownwardly to the inlet end of the colder evaporator 12c. -A conduit He provides communication between the lowerorl outlet end of the evaporator Hc direct withithe suction COIl-r duit 23c, without any valve therebetween, while a conduit I90 connects the outlet end of the colder evaporator |2c with the suction conduit 23c througha valve 51, whiclijthus controls flow of refrigerant through the evaporator Me.

In this embodiment, I show a heat exchanger 58 having one passage interposed in the suction conduit 23c and a second passage interposed in q the liquid refrigerant conduit c, thereby effecting transfer of heat from the-warm condensed refrigerant to the colder vaporized refrigerant under low pressure going to the compressor. Such heat exchangers per se are well-known in the art, and may be provided in anyof the. other embodiments. A storage chamber 59, may be provided if found desirable, for storing liquid refrigerant which may enter the suction conduit 230 at certain times, such as when beginning operation of the colder evaporator 120 after previous operation of the warmer evaporator Me. If it is found that lubricant is not drawn through the chamber 59 and accumulates therein, suitable provision may be made for removing the same when an objectionable quantity has: accumulated. An outlet 60 having a valve 6| may be provided for this purpose.

The operation of the embodiment shown in Fig. 4 is as follows: To effect refrigeration of the warmer compartment I30, the valve 51 is closed.

The compressor and condenser operate in the usual manner, as described in connection with' Fig. 1, supply condensed refrigerant to the thermostatic valve, which regulates the supply thereof to the evaporators through the conduit "5c. The conduit l6c supplies liquid refrigerant to the colder evaporator l2c to replace any vapor present from previous operation and which is now condensed. After the evaporator I20 is filled with liquid refrigerant, the mixture of vaporous and liquid refrigerant supplied through the conduit I60 is conveyed through the conduit [80 and evaporated. Liquid refrigerant is vaporized therein and the vaporous refrigerant is discharged through the conduit lie to the suction conduit 230. In the heat exchanger 58, the vaporous refrigerant extracts heat from the condensed refrigerant, and then flows on through the chamber 59 to the compressor. The thermostatic expansion valve SIc'operates to regulate the supply of refrigerant in accordance with the requirements of the evaporator Me as in Fig. 1, and the colder evaporator He is again filled with liquid refrigerant to prevent condensation of vaporous refrigerant therein, except such refrigerant as may be trapped therein from previous operation thereof, which quantity is relatively small.

To effect refrigeration in the colder compartment I lo, the valve 51 is opened to permit flow of refrigerant through the colder evaporator 12c. While both evaporators are now in communication with the suction conduit 230, the liquid refrigerant flows through the colder evaporator, due to the gravity head imposed by the conduit [8c. The refrigerant vaporized in the colder compartment We is discharged at a lower temperature, so that the thermostatic expansion valve 31c operates to maintain a lower suction pressure, supplying such quantity of refrigerant as can be completely vaporized in the colder evaporator. The refrigerant which is vaporized upon leaving the valve 310 may fiow upwardly through the conduit I80 and through the warmer evaporator I40, thereby effecting a slight degree of cooling of the warmer compartment and also slightly superheat said vapor. It is conveyed through the conduit 2|c to the suction conduit and removed along with the vaporized refrigerant removed from the colder evaporator.

When operation of the colder evaporator is begun after previous operation of the warmer evaporator, the former and the conduit I90 are filled with liquid refrigerant, so that liquid refrigerant may be drawn into the suction conduit 230 before the thermostatic valve 31c can operate to reduce the quantity of liquid refrigerant in the low side. Such liquid refrigerant is retained temporarily in the chamber 59 and slowly vaporized by the superheated vaporized refrigerant circulated therethrough.

In Fig. 5, I show an embodiment of my-invention in which a float valve 48 is provided to pass all of the refrigerant as fast as it is condensed and in which a selector valve 2201 is connected between the refrigerant supply conduit Hid and the conduits Nd and |8d connected to the colder the chamber 62 through a conduit 2| d, which is looped upwardly above the chamber 62, as shown at 63, before connecting therewith.

To effect operation of the colder evaporator 12d, the selector valve 22d is positioned to supply refrigerant thereto. Inasmuch as the quantity of liquid refrigerant supplied to the evaporator I2d is in excess of the quantity that can be contained therein, a portionthereof is drawn through the conduit l9d into the chamber 62 in which it is retained during the operation of said evaporator. Refrigerant vaporized in the evaporator is withdrawn through the conduit l9d and the chamber 62 to the suction conduit 23d. Liquid refrigerant is prevented from entering the warmer evaporator ltd through the conduit Zld because of the loop 63 formed therein. h

When the valve TM is positioned to supply refrigerant to the warmer evaporator Md, liquid refrigerant in the chamber 62 is forced by the increased suction pressure and by gravity through the conduit I9d into the colder evaporator l2d, to completely fill the same with liquid refrigerant. The remaining refrigerant in the chamber 62, which is required for operationof the warmer evaporator Md, is gradually vapor ized by the superheated vapor discharged from said evaporator. It is compressed, condensed, and supplied to the warmer evaporator to effect refrigeration therein.

In Fig. 6, I show one form of control mechanism which may be applied to any one of the above embodiments of refrigerating apparatus. This mechanism includes a thermostat T1 which is disposedin whichever refrigerated compartment isto have preference, and a thermostat T2 for the other compartment. The thermostat T1 has contacts 64 which are closed and contacts 63 which are opened when the thermostat calls for refrigeration, and the thermostat T2 isprovided with contacts 65 which are closed when the same calls for refrigeration. The contacts 64 and 65 are connected in parallel in one side of the line going to a starting relay 66. The starting relay is connected to the compressor motor 28 by the necessary number of conductors, including com ductors 61 connected to the running winding of the motor. A circuit 68 extends from one of they conductors 67 through the coil 25 and the contacts 63 to the other conductor 61. The core 24 actuated by the solenoid coil 25 is connected to the valve 22 in such manner that, when the coil is not energized, the spring 26 positions the valve 22 so that refrigerant is circulated to that evaporator which is to have preference when both evaporators are calling for refrigeration, and so that, when the coil 25 is energized, the valve 22 is positioned to circulate refrigerant to the other evaporator.

The operation of this controLmechanism is as follows: Assume that this control system is applied to the apparatus shown in Fig. 1, that the thermostat T1 is located in the colder compartment ii to give the same preference and that the thermostat T2 is located in the warmer compartment l3. The core 24 and the valve 22 are connected as in Fig. 1. Assuming that the warmer compartment is calling for refrigeration and that the other is not, the contacts 65 and 63 are closed and the contacts opened, as shown in Fig. 6. The closing of the contacts 65 effects energization of the compressor motor, and of the conductors 61. The contacts63being closed, the circuit 68 is now closed to energize the coil 25, thereby ositioning the valve to circulate refrigerant th ugh the warmer evaporator l 4.

When the thermostat T1 in the colder compartment calls for refrigeration, the contacts 64 are closed and the contacts 63 opened. The contacts 64 effect energization of the motor and of the conductors 61, but,in this case, the contacts 63 prevent energization of the solenoid 25, regardless of whether the thermostat T2 is calling for refrigeration. The valve 22 is thus positioned to circulate refrigerant through the colder evaporator. When the refrigeration demand of the colder compartment is satisfied, the contacts 63 are closed to enable the thermostat T2 to effect refrigeration in the warmer compartment.

With this embodiment, it will be noted that the Valve 22 is positioned for circulation of refrigerant through the preferred evaporator when neither thermostat is calling for refrigeration.

In Fig. 7, I show another form of control mechanism comprising thermostats Tl and T2 which operate contacts 64 and 65, respectively, asin Fig. 6, but in which the thermostat Trcloses contacts 63 when calling for refrigeration. In this case, the core 24 is connected to the, valve in such manner that refrigerant is circulated through the preferred evaporator when the coil 25 is energized, since the contacts 63' close the circuit 68 when the preferred thermostat T1 calls for refrigeration. The core and valve are biased to the opposite position by a tension spring 26' when the coil is deenergized.

The operation of this embodiment is as follows: When the thermostatTi calls for refrigeration, the contacts 64 effect energization of the compressor motor 28 and the contacts 63'energize the coil 25 to circulate refrigerant through the preferred evaporator, regardlessof whether the other evaporator requires refrigeration. When the thermostat T2 calls for refrigeration, the contacts 65 effect energization 'of'the compressor motor 28, but refrigerantwilLbe circulated, to thesecond evaporator associatedtherewith only when the thermostat Ti'becomes satls fied and opens the contacts 69'. With this embodiment, the valve 22 is positioned for circulation of refrigerant to the non-preferred evaporator when neither thermostat calls for refrigeration.

In Fig. 8,I show a third form of control mechanism in which the thermostat Ta is provided with contacts 69 in series with the 001125 and in a series with the compressor motor 28. Themeferred thermostat T1 is provided with contacts H' which are connectedin parallelwith thecoil 25 and the contacts 69 and in series with the motor 28. When the thermostat T2 calls for refrigeration and thethermostat T1 does not, the contacts 69 close a circuit through the coil 25, the

contacts 69, and the motor 28 in series, thereby effecting refrigeration in the non-preferred'evaporator. When the thermostat Tl. closesthe contacts H, the compressormotor 28 is energized,

while the coil 25 is deenergized regardless of whether the contacts 69 are closed, since the current through the coil is shunted to the contact H, andthe core 24' and the valve 22 are posi-' 7 tioned by the compression spring 26 for opera-" tion of the preferred evaporator. In this case, the core 24 is connected to the valve 22 in such manner that refrigerant is circulated through the preferred evaporator when the coil is not energized. I

It will be noted that any one of the three forms of control mechanisms shown in Figs. 6, 7, and

8 may be applied to any one of the embodiments of refrigerating mechanism by merely connecting the solenoid in correct relation to the selector valve 22.

In each of the above embodiments, the portions of the low side conduits outside the refrigerated compartments are preferably heatinsulated or arranged in some suitable way to fore desire that only such limitations shall be placed thereupon as are imposed by the prior art.

or as are set forth in the appended claims.

'What I claim is: v

1. In a refrigerating system, the combination of a lower temperature and a highcrtempera- 'ture evaporator connected in parallel and in unrestricted communication with each other so that the pressure therein is substantially the same at all times, means including a compressor and a condenser for effecting evaporation of liquid refrigerant in said evaporators and for supplying liquid refrigerant thereto, said means being operative to effect evaporation of liquid refrigerant in the higher temperature evaporator at a temperature above the temperature of the lower temperature evaporator and at a pressure higher than the pressure corresponding to said temperature of the lower temperature evaporator, means common to said evaporators for reducing the pressure of the liquid refrigerant supplied thereto, and valve means for controlling flow of refrigerant through at least one evaporator for selectively effecting refrigeration in either evaporator, said evaporators being connected in such manner that liquid refrigerant flows into the lower temperature evaporator in preference to the higher temperature evaporator.

2. In a refrigerating system, the combination of a lower temperature and a higher temperature evaporator, means for compressing and condensing refrigerant vaporized in said evaporators, means common to said evaporators for reducing the pressure of the condensed refrigerant, means for conveying liquid refrigerant from the pres sure-reducing means to said evaporators, said conveying means providing unrestricted communication between said evaporators at all times and being arranged so that liquid refrigerant flows into the lower temperature evaporator in preference to the higher temperature evaporator, and valve means for controlling flow of vaporized refrigerant from at least one evaporator to the compressing means for selectively effecting refrigeration in either evaporator, said conveying mean's serving to maintain the higher temperature evaporator substantially dry while said valve means is adjusted to effect refrigeration in the lower temperature evaporator.

3. In a refrigerating system, the combination of a lower temperature and a higher temperature evaporator, means for compressing and condensing refrigerant vaporized in said evaporators, means common to said evaporators for reducing the pressure 'of the condensed refrigerant, means conveying refrigerant from the pressure reducing means, said conveying means providing unrestricted communication between said evaporators and being arranged so that liquid refrigerant fiows into the lower temperature evaporator in preference to the higher temperature evaporator, and valve means for selectively providing communication between the vapor outlet of either evaporator and the compressing means and shu ting off flow from the vapor outlet of the other evaporator.

-4.In a refrigerating system, the combination of a lower temperature and a higher temperaturev evaporator, a compressor, a condenser, means for conveying condensed refrigerant from the condenser to said evaporators, a thermostatic expansion valve in a portion of said conveying means common to said evaporators, means for conveying vaporized refrigerant from said evaporators to the inlet of said compressor, means responsive to the temperature of a portion of said conveying means common to said evaporators for governing the operation of said thermostatic expansion valve, and means for selectively effecting refrigeration in either evaporator.

5. In a refrigerating system, the combination of a low temperature and a higher temperature evaporator, a compressor, a condenser, means for conveying condensed refrigerant from the condenser to said evaporators, a thermostatic expansion valve in a portion of said conveying means common to said evaporators, means for conveying vaporized refrigerant from said evaporators to the inlet of said compressor, means responsive to the temperature of a portion of said conveying means common to said evaporators for governing the operation of said thermo static expansion valve, and valve means for providing circulation of refrigerant through either evaporator and for shutting off circulation thereof through the other evaporator, whereby refrigeration may be selectively effected in either evaporator.

6. In a refrigerating system, the combination of a lower temperature and a higher temperature evaporator, a compressor, a condenser, means for conveying condensed refrigerant from the condenser to said evaporators, means for controlling the flow and reducing the pressure of the refrigerant in a portion of said conveying means common to said evaporators, and means for selectively placing the vapor outlet of either evaporator in communication with the inlet of said compressor for selectively providing refrigeration in either evaporator, and means whereby,

when the higher temperature evaporator is in operation, the lower temperature evaporator only receives liquid refrigerant when the same is in operation and whereby the lower temperature evaporator is filled with a static body of liquid refrigerant and liquid refrigerant is supplied to the higher temperature evaporator and evaporated therein at a temperature above the temperature of the lower temperature evaporator and at a pressure higher than the pressure corresponding to said temperature of the lower temperature evaporator. V

7. In a refrigerating system, the combination of a lower temperature and a higher temperature evaporator, a compressor, a condenser means for conveying condensed refrigerant from' the condenser to said evaporators, means for controlling the flow and reducing the pressure of the refrigerant in a portion of said conveying means mon to said evaporators, and means for selectively supplying liquid refrigerant to the low temperature evaporator and preventing the admission of appreciable quantity of liquid refrigerant to the high temperature evaporator, for operation of the low temperature evaporator, or supplying liquid refrigerant to the higher temperature evaporator and effecting evaporation therein at a temperature above the temperature of the lower temperature evaporator and at a pressure higher than the pressure corresponding to said temperature of the lower temperature evaporator while maintaining the lower temperature evaporator substantially filled with a static head of liquid refrigerant.

8. In refrigerating apparatus, the combination of a lower temperature evaporator and a higher temperature evaporator, means for liquefying refrigerant, means for conveying liquidrefrigerant from said liquefying means to said evaporators, a valve in a portion of said conveying means common to both evaporators, means for conveying vaporized refrigerant from said evaporators to said liquefying means, means responsive to the temperature of the refrigerant in a portion of the last-mentioned means common to said evaporators for controlling said valve so as to pass such quantity of refrigerant as is be ing evaporated in whichever evaporatoris effective, and means for selectively effecting refrigeration in either evaporator.

9. In a refrigerating system, the combination of a low temperature and a higher temperature evaporator: a compressor, a condenser, means flow of liquid refrigerant from said supply means to said warmer evaporator, and a connection providing unrestricted communication at all times between said evaporators and the inlet of said compressor and arranged so that liquid refrigerant fiows into the colder evaporator in preference to the warmer evaporator and through which connection vaporized refrigerant flows from the colder evaporator during operation thereof and from the warmer evaporator during operation thereof, said connection serving to prevent liquid refrigerant entering the warmer evaporator when said valve is closed.

18. In a refrigerating system, the combination of a colder evaporator and a warmer evaporator, means including a compressor and a condenser for effecting evaporation of liquid refrigerant in said evaporators and for supplying liquid refrigerant thereto, the warmer evaporator having an inlet and an outlet through which refrigerant respectively' enters and leaves while evaporation of refrigerant is eflected therein, a valve control ling flow of liquid refrigerant from said supply means to the inlet of the warmer evaporator, and

means providing unrestricted communication at all times between the colder evaporator, the outlet of the warmer evaporator, and the inlet of the compressor and arranged so that liquid refr1gerant flows therefrom to the colder evaporator in preference to the warmer evaporator, said lastmentioned means serving to prevent liquid refrigerant entering the warmer evaporator while said valve is closed.

LESLIE B. M. BUCHANAN. 

